Nintendo has posted a tweet indicating that Pokémon Bank has launched in certain Asian countries. Nintendo and The Pokémon Company International postponed the launch of Pokémon Bank and Poké Transporter which initially launched on December 27th, 2013 but was pulled after a few hours on the eShop due to a large volume of traffic to the Nintendo Network service.
Nintendo also posted a second tweet indicating that they will be informing users soon about Pokémon Bank's availability in North America and other regions of the world.
Source:
https://twitter.com/NintendoAmerica/status/425815499956445184 and
https://twitter.com/NintendoAmerica/status/425815578436059136